The surface radio frequency (rf) power absorption in human head and torso nuclear magnetic resonance (NMR) imaging experiments is estimated. The results are expressed as a function of the NMR frequency, the rf pulse length, and the pulse duty cycle, which are varied over six orders of magnitude for general applicability. The results are compared with average metabolic levels and the limits advised by the National Radiological Protection Broad of the United Kingdom. Heating due to time-dependent magnetic field gradients is discussed.